Variable frequency stimulation (VFS) is a new mode of sacral neuromodulation (PINS, China), which can provide alternating electrical stimulation between high and low frequencies according to the clinical symptoms of patients, and automatically change the frequency during the stimulation process. The aim of this study is to evaluate the efficacy and safety of VFS in the treatment of overactive bladder (OAB) symptoms.

A prospective, randomized, blinded, 2×2 cross-controlled study was conducted. Successfully enrolled patients had the device switched off for 7±3 days (baseline period). Then the patients were randomly divided into group A and group B according to the ratio of 1:1. The patients in group A were treated according to the sequence of constant frequency stimulation (CFS) - shutdown-VFS, and the patients in group B were treated according to the sequence of VFS -shutdown-CFS. The patients were followed up at 6, 12, 18 and 24 weeks, and the stimulation mode was changed at 12 weeks. The voiding diary, subjective scores, patient satisfaction and adverse events were collected at baseline and each follow-up point to evaluate the efficacy and safety of VFS.

A total of 57 patients were enrolled, including 29 patients in group A and 28 patients in group B. There was no significant difference in demographic data between the two groups. At the 24th week, the micturition frequency of group A and group B decreased by 7.26±7.68 times (p=0.001) and 3.18±4.04 times (p=0.001), respectively, which were significantly improved compared with the baseline period, and there was a significant difference between the two groups (p=0.017). At the 24-week follow-up, the urination volume, urinary incontinence times and subjective scores in Group A and Group B were significantly improved compared with the baseline (all p<0.05), but there was no significant difference between the two groups (all p>0.2). The incidence of adverse events was 5.26%.

The VFS mode of SNM is not inferior to traditional CFS mode in the improvement of OAB symptoms, which can effectively improve the symptoms of patients. However, the most suitable stimulation parameters for different patients still need to be studied.